Hemostasis valves are used on hemostasis cannulas, such as catheter introducers which are presently in medical use for assisting in the insertion of angiographic catheters into the arterial system of a patient. Such hemostasis cannulas carry a rubber gasket hemostasis valve, which permits a catheter to pass through the gasket into the catheter introducer or other cannula while preventing blood leakage. Examples of patents which cover such hemostasis cannulas include Stevens U.S. Pat. No. 4,000,739, Weinstein U.S. Pat. No. 4,626,245, Matsumoto et al. U.S. Pat. No. 4,610,665, and Hillstead U.S. Pat. No. 4,798,594 among others.
In accordance with this invention, an improved hemostasis valve is provided in which a novel configuration is provided in the elastic gasket of the hemostasis valve. This configuration provides improved performance, including easy catheter advancement coupled with good sealing, to prevent the back leakage of blood when the cannula, on which the hemostasis valve is carried, is in communication with an artery, whether or not a catheter is extending through the valve.